1. Field of the Invention
The present invention relates to receiving apparatuses and transmission apparatuses utilizing the same, and it particularly relates to a receiving apparatus using the current as a means for transmitting signals and a transmission apparatus utilizing the same.
2. Description of the Related Art
An electronic device is generally made up of a plurality of circuits, such as a central processing unit and semiconductor integrated circuits. For instance, a cellular phone is composed of a communication circuit, a display and an image shooting device. The circuits constituting an electronic device perform their respective processings; that is, a communication circuit carries out communication processing, a display displays predetermined types of information, and an image shooting device carries out image processing. And these circuits further process transmission of signals to and from the other circuits. The image shooting device, for example, transmits data of images shot to the communication circuit. And in the transmission of signals between circuits, the medium used in the conventional practice has been voltage, which changes its value between the power-supply voltage and the ground voltage. However, as the use of higher operating speeds for circuits and larger-capacity processing of signals by a central processing unit has increased in recent years, the signal transmission by means of the voltage began to pose a problem as mentioned below when raising the processing speed for signal transmission between circuits.
In general, a signal transmission line between circuits has a capacitance, and an electric charge is charged or discharged according to the capacitance when the voltage changes. Hence, transmission of signals by the medium of voltage involves extra time for charging and discharging the electric charge due to the capacitance. As a result, the time taken for the rise and fall of signals makes it difficult to achieve the high-speed signal transmission. To solve this problem, a signal transmission technology has been proposed in which current, instead of voltage, is used in transmitting signals.
Related Art List
(1) Japanese Patent Application Laid-Open No. 2001-53598.
Transmission of signals by the medium of current does not require the generation of a significant potential difference as in the case of signal transmission by the medium of voltage. This will result in a reduced amount of electric charge to be charged and discharged, thus making it possible to achieve higher speeds for signal transmission. However, to further raise the speed of signal transmission by current, it is preferable that the voltage variation to be caused by the signal transmission by current be further reduced.
In the case of a foldable cellular phone whose structure is such that the casing is separated into a part including a display and an image shooting device and another part including a communication circuit, the signal transmission lines are arranged such that they are positioned on both sides of the movable mechanism therebetween. As the amount of data to be transmitted increases due to the higher accuracy of the image shooting device and so forth, the number of signal transmission lines to be provided tends to increase accordingly. However, the number of the lines must be held low in consideration of the degree of freedom in arrangement of the signal transmission lines at the movable mechanism, which performs folding or rotating motion. In general, as the number of signal transmission lines decreases, the reliability of the movable mechanism which performs complex operations is raised. As a result of reduction in the number of signal transmission lines, a higher speed of signal transmission is required for each of the signal transmission line.